The present invention provides a method for preparing high vinylidene polyisobutylene by polymerizing isobutylene with a solid catalyst of a calcined ammonium salt of a heteropolyacid.
It is well known to polymerize olefins using boron trifluoride (BF3). The polymers so produced are highly reactive due to a large percentage of their terminal groups having vinylidene structure. The reactivity of polyolefins has been related to double bond content and the location thereof in the polymer.
U.S. Pat. No. 4,152,499, Boerzel et al., May 1, 1979, discloses the synthesis of polyisobutylene polymers having a degree of polymerization of 10 to 100 units and a high proportion of reactive double bonds. The isobutene is polymerized with boron trifluoride as the initiator at xe2x88x9250xc2x0 C. to +30xc2x0 C. The polymer contains a proportion of double bonds capable of reacting with maleic anhydride of 60 to 90% of theory. The adducts from the polyisobutylene/maleic anhydride are reacted with polyamines to form products useful as lubricating oil additives.
Polyolefins have also been prepared by polymerization catalyzed with heteropolyacids. U.S. Pat. No. 5,710,225, Johnson et al., Jan. 20, 1998, discloses a method for producing polymers by polymerization of olefins, by contacting a C2-C30 olefin or derivative thereof with a heteropolyacid. The heteropolyacid catalyst can be a partially or fully exchanged with cations from the elements in groups IA, IIA and IIIA of the periodic chart, Group IB-VIIB elements and Group VIII metals, including manganese, iron, cobalt, nickel, copper, silver, zinc, boron, aluminum, bismuth, or ammonium or hydrocarbyl-substituted ammonium salt. The heteropolyacids can be used in their initial hydrated form or they can be treated (calcined) to remove some or all of the water of hydration. The calcining is preferably conducted in air at a temperature of, for instance, up to 375xc2x0 C.; temperatures much over 350xc2x0 C. do not generally provide much advantage. In the resulting polymers, the combined terminal vinylidene and xcex2-isomer content is preferably at least 30%.
U.S. Pat. No. 2,982,799 (Klinkenberg, May 2, 1961) reports that at about 20-200xc2x0 C. isobutylene can be polymerized by use of a specially prepared heteropolyacid catalyst. The catalyst consisted of a heteropolyacid deposited on a solid carrier. The solid carrier had an alkali (including ammonium) content of less than one milliequivalent per 100 grams of carrier and a silico-tungstic acid concentration of 0.5-8% by weight of the total catalyst. The system resulted in oligomers up to C16 from isobutylene, or a degree of polymerization of four. The temperature used was above 20xc2x0 C.
It is believed to be desirable to use highly reactive polyolefins to prepare hydrocarbyl-substituted acylating agents (e.g., anhydrides) by way of a thermal route rather than a chlorine catalyzed route. The thermal route avoids products containing chlorine. The reactivity of the polyolefin is believed to be related to the end group in the polymer with terminal olefins (terminal vinylidene) and terminal groups capable of being isomerized thereto being identified as the reactive species. The groups capable of being isomerized to the terminal vinylidene (I) group are the xcex2-isomers (II) of Table 1.
As used herein, the term xe2x80x9chydrocarbyl substituentxe2x80x9d or xe2x80x9chydrocarbyl groupxe2x80x9d is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include hydrocarbon substituents, substituted hydrocarbon substituents, and hetero substituents, that is, substituents which, while having a predominantly hydrocarbon character, contain other than carbon in a ring or chain otherwise composed of carbon atoms. In general, no more than two, preferably no more than one, non-hydrocarbon substituents will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituents in the hydrocarbyl group.
Conventional polyolefin synthesis involves Friedel-Crafts type catalysts reacting with terminal olefins such as isobutene or mixtures of compounds such as a C4 raffinate from a cat cracker or an ethylene plant butane/butene stream. The polyolefins so synthesized are not noted for having high terminal vinylidene contents and are thus not the reagents of choice to use the thermal route to forming polyolefin substituted succinic anhydrides. Conventional polyisobutylene (xe2x80x9cPIBxe2x80x9d) when used in thermal condensation procedures with maleic anhydride give low yields and high tar contents and low succination ratios. The thermal route to substituted succinic anhydrides using highly reactive PIB""s has been discussed in detail in U.S. Pat. Nos. 5,071,919, 5,137,978, 5,137,980 and 5,241,003, all issued to Ethyl Petroleum Additives, Inc.
The isomer content of a conventional (AlCl3) and high terminal vinylidene PIB""s are shown in Table 1. Conventional PIB has terminal vinylidene content of roughly 5%. The terminal isomer groups of conventional PIB and high vinylidene PIB are given below in Table 1 and those published in EPO 0355 895. However, in this invention polyisobutylene containing relatively high content of vinylidene and xcex2-isomers can be formed. Such materials can contain at least 30 percent terminal vinylidene (I) and xcex2-isomer (II) groups, as shown below. In preferred cases the polyisobutylene can contain at least 30 percent terminal vinylidene (I) groups, and more preferably at least 60 percent terminal vinylidene groups.
As can be seen from the structures in Table 1, conventional PIB is characterized by very low terminal vinylidene groups (I) and species capable of isomerization therewith (II). Conventional PIB further comprises a distinct tri-substituted terminal olefin group (III) which is nearly absent or present in only a low level in high vinylidene PIB. The distinct terminal group III is a 2-butene in which the 2-carbon is tri-substituted.
Structure IVA of Table 1 is an acid-catalyzed rearrangement product of IV while V is an internal vinylidene group. The terminal group content of conventional and high vinylidene PIBs have been determined by NMR analysis. Conventional PIBs are commercially available under various tradenames including Parapol(copyright) from Exxon, Lubrizol(copyright) 3104, 3108 from Lubrizol and Indopol(copyright) from Amoco and Hyvis(copyright) from BP. Conventional PIBs have number average molecular weight in the range of 300-5000, but the preferred number average molecular weight is in the range of 500-2000.
The present invention provides a method for producing polymers by polymerization of at least one olefin, the method comprising:
contacting (a) at least one C2-C30 olefin or polymerizable derivatives thereof with (b) a catalyst comprising a partially or fully neutralized ammonium salt of a heteropolyacid,
wherein said catalyst has been calcined at above 350xc2x0 C. to 500xc2x0 C.;
whereby the efficiency of polymerization is increased compared to the efficiency in the absence of such calcining.
The present invention further provides polymers of isobutylene having a {overscore (M)}n of at least 1500, {overscore (M)}w/{overscore (M)}n of greater than 4, preferably 7.5 to 20, and preferably at least 30% terminal vinylidene (I) groups.
Heteropolyacid catalysts can exist as the free acid or as a salt of a heteropolyanion. Heteropolyanions are polymeric oxoanions formed by a condensation reaction of two or more different oxoanions, e.g.,
12WO42xe2x88x92+HPO42xe2x88x92+23H+xe2x86x92(PW12O40)3xe2x88x92+12H2O
A variety of structures are known for these materials; they can have, for instance, the so-called Keggin structure, wherein twelve WO6 octahedra surround a central PO4 tetrahedron (in the case where phosphorus is employed). Other structures and related formulas are also known, including PW12O42, PW18O62, P2W5O23, PW9O32, PW6O24, P2W18O62, PW11O39, and P2W17O61, where P and W are taken as representative elements and the indicated structure is an ion with the appropriate charge. The central atom of the Keggin structure, which is typically phosphorus, as shown, can also be any of the Group IIIA to Group VIIA (ACS numbering) metalloids or non-transition metals, including P, As, Si, Ge, B, Al, Sb, and Te. The tungsten (W) in the above formula fills the role known as the xe2x80x9cpoly atom,xe2x80x9d which can be any of the Group VB or VIB transition metals, including W, V, Cr, Nb, Mo, or Ta. Thus suitable materials include preferably phosphomolybdates, phosphotungstates, silicomolybdates, and silicotungstates. Other combinations selected from among the above elements are also possible, including borotungstates, titanotungstates, stannotungstates, arsenomolybdates, teluromolbydates, aluminomolybdates, and phosphovanadyltungstates, the latter representing a mixed material having a formula (for the anion portion) of PW11VO40. The preferred material is a phosphotungstate, which term generally encompasses both the acid and the various salts, described below.
The heteropoly catalysts are active both as their acid form, in which the anion is associated with the corresponding number of hydrogen ions, in the fully salt form, in which the hydrogen ions have been replaced by other cations such as metal ions, or in the partially exchanged salt form, in which a portion of the hydrogen ions have been thus replaced. For more detailed information on the structures of heteropoly catalysts, attention is directed to Misono, xe2x80x9cHeterogeneous Catalysis by Heteropoly Compounds of Molybdenum and Tungsten,xe2x80x9d Catal. Rev.xe2x80x94Sci. Eng., 29(2and3), 269-321 (1987), in particular, pages 270-27 and 278-280. In the present invention, the hydrogen ions have been partially or fully replaced by ammonium, that is the catalyst is a partially or fully neutralized ammonium salt of a heteropolyacid. Moreover, the catalyst has been calcined at above 350xc2x0 C. to 500xc2x0 C.
Heteropoly acids are commercially available materials, (e.g., Aldrich Chemical Company, #22,420-0). The salts are similarly commercially available. Alternatively, they can be prepared from the acid materials by neutralization with an appropriate amount of base. Heteropoly acids are generally received in a hydrated form. They can be successfully employed in this form (uncalcined) or as in the present invention, they can be treated (calcined) to remove some or all of the water of hydration, that is, to provide a dehydrated or otherwise modified species, which in the context of the present invention exhibits improved reactivity. Calcining can be conducted by simply heating the hydrated material to a suitable temperature to drive off the desired amount of water. The heating can be under ambient pressure or reduced pressure, or it can be under a flow of air or an inert gas such as nitrogen. The use of air ensures that the acid is in a high oxidation state. The flow of air can be across the surface of the catalyst, or for greater efficiency, it can be through the bulk of the catalyst. The length of time required for calcining is related to the equipment and scale, but in one broad embodiment the calcining can be conducted over the course of 5 minutes to 16 hours, more typically 30 minutes to 8 hours, and preferably 1 hour, 2 hours or even 3 hours, up to 4 hours. The upper limits of time are defined largely by the economics of the process; times in excess of about 5 hours do not generally provide much advantage.
The material which is calcined to prepare the catalysts for use in the present invention is preferably an ammonium salt of H3PW12O40. Typical ammonium salts include (NH4)3PW12O40 and (NH4)2.5H0.5PW12O40. While generally the temperature of calcining will be in the range of above 350xc2x0 C. to 500xc2x0 C. and preferably 375 to 475xc2x0 C., the optimum conditions will depend to some extent on the particular ammonium salt which is selected. When the starting salt is (NH4)3PW12O40, it has been found that relatively higher temperatures are desirable for obtaining the most active catalyst. Therefore, such material is preferably calcined at 450 to 475xc2x0 C. When the starting salt is (NH4)2.5H0.5PW12O40, desirable calcining temperatures can be somewhat lower, namely, above 350 to 475xc2x0 C. and preferably above 375 to 475xc2x0 C. When the calcining temperature is too low, the catalysts may be largely or entirely inactive. For instance, when (NH4)3PW12O40 is treated at below 350xc2x0 C., it is generally found to be substantially inactive to provide the polymers of the present invention. This phenomenon is not fully understood; but, without intending to limit the generality or scope of the invention, it is believed that the high temperature calcining serves to remove a portion of the ammonia from the catalyst, thereby leading to a more active species. The time and temperature of the calcining are believed to be interrelated to some extent, so that use of temperatures in the lower ranges can be more effective when the calcining is conducted for a longer period of time, and vice versa, as will be apparent to the person skilled in the art.
The catalyst can be employed as particles of the pure salt, or it can be provided on a solid support of an inert material such as alumina, silica/alumina, an aluminophosphate, a zeolite, carbon, clay, or, preferably, silica. The source of the solid silica support can be a colloidal silica, which is subsequently precipitated during the catalyst preparation, or a silica which has already been preformed into a solid material. The catalyst can be coated onto the support by well-known catalyst impregnation techniques, e.g., by applying the catalysts as a solution, followed by drying, such as by spray drying or evaporation. If a support such as silica is employed, the ratio of the active catalyst component to the silica support will preferably be in the range of 0.5:99.5 to 50:50 by weight, preferably 3:97 to 40:60 by weight, and more preferably 10:90 to 30:70 by weight.
The temperatures used in this invention for the polymerization of olefins is preferably below 20xc2x0 C. and more preferably below 10xc2x0 C. Preferred temperature ranges are xe2x88x9230 to 20xc2x0 C., more preferably xe2x88x9220 to 10xc2x0 C. and most preferably about xe2x88x925xc2x0 C., which is the approximate reflux temperature of isobutylene. The polymerization can be conducted in a batch apparatus or using continuous apparatus, such as a continuous stirred tank reactor or a tubular reactor, as will be apparent to those skilled in the art. The residence time of the polymerization reaction will vary with conditions including the type of reactor. Generally suitable residence times of 5 or 10 to 60 minutes, preferably 20 to 40 minutes. The polymerization can be conducted neat but is preferably conducted in the presence of a substantially inert hydrocarbon solvent or diluent, such as isobutane, pentane, hexane, octane, decane, kerosene, or Stoddard Solvent, which will normally be removed by conventional means at the conclusion of the reaction. The reaction using the catalysts of the present invention will generally provide at least a 10% conversion under these conditions, and preferably at least 20 or 25% conversion to polymer.
The preferred products are polyisobutylenes having {overscore (M)}n greater than 300. For the C4 isobutylene, this would correspond to an average degree of polymerization (dp) of about 5.3. The preferred {overscore (M)}n of polyisobutylene is at least 500 and more preferably at least 1000 or 1500, and up to 5,000, preferably in the range of 2000 to 5000. Such materials are particularly useful when used in reactions to alkylate maleic anhydride and for subsequent derivatization to form, e.g., imides, for use as additives for lubricants, as is well known to those skilled in the art. As well as isobutylenes, other C2-C30 olefins and derivatives thereof may be used in this invention as well as styrene and derivatives thereof, conjugated dienes such as butadiene and isoprene and non-conjugated polyenes. The reaction to produce polymers may be run with mixtures of starting olefins to form copolymers. The mole ratio of olefin substrate to catalyst in this invention ranges from 1,000:1 to 100,000 to 1.
The polymers produced by the process of this invention are derived from C2-C30 olefin monomers and mixtures thereof and derivatives thereof. Under this terminology, styrene and derivatives would be a C2-olefin substituted by a phenyl group.
Useful olefin monomers from which the polyolefins of this invention can be derived are polymerizable olefin monomers characterized by the presence of one or more unsaturated double bonds (i.e.,  greater than Cxe2x95x90C less than ); that is, they are monoolefinic monomers such as ethylene, propylene, butene-1, isobutylene, and octene-1 or polyolefinic monomers (usually diolefinic monomers) such as butadiene-1,3 and isoprene.
These olefin monomers are preferably polymerizable terminal olefins; that is, olefins characterized by the presence in their structure of the group xe2x80x94Rxe2x80x2xe2x80x94CHxe2x95x90CH2, where Rxe2x80x2 is H or a hydrocarbyl group. However, polymerizable internal olefin monomers (sometimes referred to in the patent literature as medial olefins) characterized by the presence within their structure of the group: 
can also be used to form the polyalkenes. When internal olefin monomers are employed, they normally will be employed with terminal olefins to produce polyalkenes which are interpolymers. For purposes of this invention, when a particular polymerized olefin monomer can be classified as both a terminal olefin and an internal olefin, it will be deemed to be a terminal olefin. Thus, for example, pentadiene-1,3 (i.e., piperylene) is deemed to be a terminal olefin for purposes of this invention.
While the polyalkenes of this invention generally are hydrocarbon polyalkenes, they can contain substituted hydrocarbon groups such as lower alkoxy, and carbonyl, provided the non-hydrocarbon moieties do not substantially interfere with the functionalization reactions of this invention. Preferably, such substituted hydrocarbon groups normally will not contribute more than 10% by weight of the total weight of the polyalkenes. Since the polyalkene can contain such non-hydrocarbon substituents, it is apparent that the olefin monomers from which the polyalkenes are made can also contain such substituents. Normally, however, as a matter of practicality and expense, the olefin monomers and the polyalkenes will be free from non-hydrocarbon groupsxe2x80x94(as used herein, the term xe2x80x9clowerxe2x80x9d when used with a chemical group such as in xe2x80x9clower alkylxe2x80x9d or xe2x80x9clower alkoxyxe2x80x9d is intended to describe groups having up to seven carbon atoms.)
Although the polyalkenes of this invention may include aromatic groups (especially phenyl groups and lower alkyl- and/or lower alkoxy-substituted phenyl groups such as para-(tert-butyl)phenyl) and cycloaliphatic groups such as would be obtained from polymerizable cyclic olefins or cycloaliphatic substituted-polymerizable acrylic olefins, the polyalkenes usually will be free from such groups. Again, because aromatic and cycloaliphatic groups can be present, the olefin monomers from which the polyalkenes are prepared can contain aromatic and cycloaliphatic groups.
There is a general preference for polyalkenes which are derived from the group consisting of homopolymers and interpolymers of terminal hydrogen olefins of 2 to 16 carbon atoms. A more preferred class of polyalkenes are those selected from the group consisting of homopolymers and interpolymers of terminal olefins of 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms.
Specific examples of terminal and internal olefin monomers which can be used to prepare the polyalkenes of this invention include propylene; butene-1; butene-2; isobutylene; pentene-1; hexene-1; heptene-1; octene-1; nonene-1; decene-1; pentene-2; propylene-tetramer; diisobutylene; isobutylene trimer; butadiene-1,2; butadiene-1,3; pentadiene-1,2; pentadiene-1,3; isoprene; hexadiene-1,5; 2-chloro-butadiene-1,2; 2-methyl-heptene-1; 3-cyclohexylbutene-1; 2-methyl-5-propyl-hexene-1; pentene-3; octene-4; 3,3-dimethyl-pentene-1; styrene; 2,4-dichlorostyrene; divinylbenzene; vinyl acetate; allyl alcohol; 1-methyl-vinyl acetate; ethyl vinyl ether; and methyl vinyl ketone. Of these, the hydrocarbon polymerizable monomers are preferred and of these hydrocarbon monomers, the terminal olefin monomers are particularly preferred.
Useful polymers formed in this invention include alpha-olefin homopolymers and interpolymers, and ethylene/alpha-olefin copolymers and terpolymers. Specific examples of polyalkenes include polypropylene, polybutene, ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, styrene-isobutylene copolymer, isobutylene-butadiene-1,3 copolymer, propene-isoprene copolymer, isobutylenechloroprene copolymer, isobutylene-(para-methyl)styrene copolymer, copolymer of hexene-1 with hexadiene-1,3, copolymer of octene-1, copolymer of 3,3-dimethyl-pentene-1 with hexene-1, and terpolymer of isobutylene, styrene and piperylene. More specific examples of such interpolymers include copolymer of 95% (by weight) of isobutylene with 5% (by weight) of styrene; terpolymer of 98% of isobutylene with 1% of piperylene and 1% of chloroprene; terpolymer of 95% of isobutylene with 2% of butene-1 and 3% of hexene-1; terpolymer of 60% of isobutylene with 20% of pentene-1; and 20% of octene-1; terpolymer of 90% of isobutylene with 2% of cyclohexene and 8% of propylene; and copolymer of 80% of ethylene and 20% of propylene. U.S. Pat. No. 5,334,775 describes polyolefin based polymers of many types and their monomer precursors and is herein incorporated by reference for such disclosure.
Relative amounts of end units in conventional and high vinylidene polyisobutylenes are determined from NMR spectra made using a Burker AMX 300 or 500 instrument and UXNMRP software to work up the spectra. The spectra are determined at 300 or 500 MHz in CDCl3. Band assignments in the NMR for the various isomers as parts per million (ppm) down field shift from tetramethyl silane are: terminal vinylidene 4.68 and 4.89, xcex2-isomer 5.18, tri-substituted 5.17 and 5.35, tetra 2.88.
The molecular weight of the isomers are typically determined by GPC on a Waters 150 instrument run with tetrahydrofuran solvent. The columns are Waters ultra-styrogel of pore size 104 xc3x85, 103 xc3x85, 500 xc3x85, and 300 xc3x85 which have been calibrated with PIB standards. Styrene molecular weight standards are also useful. {overscore (M)}n and {overscore (M)}w are determined from comparative elution volume data. Molecular weight values of the polymers produced by the method of this invention will vary according to their degree of polymerization. The dp range for products of this invention typically range from 6 to 350 or even higher.
The polydispersity of the products of this invention as determined by the ratio of {overscore (M)}w/{overscore (M)}n may have a value of up to 20 depending upon reaction conditions. At any given reaction temperature, the {overscore (M)}w/{overscore (M)}n is controlled by the chemical nature of the catalyst as well as the contact time of the olefin with the catalyst and the concentration of the olefin during the reaction. Use of the calcined ammonium catalysts of the present invention in the polymerization of isobutylene leads to polyisobutylene having a polydispersity typically greater than 4, or 5, often 7.5 to 20, more commonly 8 to 19 or 18. The present invention provides a way of preparing such materials directly, from a single polymerization reaction, as opposed to by blending of different batches prepared from separate polymerization reactions. It is, of course, well known to prepare polymeric mixtures of high polydispersity by physical admixture of samples of polymers of significantly different molecular weights. Such blending, however tends to produce polymeric mixtures which are polymodal (including bimodal) or otherwise non-uniform in their molecular weight distribution. The process of the present invention, on the other hand, can lead to polymers having a relatively uniform or monomodal molecular weight distribution, yet having the present high degree of polydispersity.